(1) Field of the Invention
The present invention relates in general to a toroidal type continuously variable transmission, and more particularly to a system for lubricating a reverse sensor of such transmission.
(2) Description of the Prior Art
As is known, a toroidal type continuously variable transmission has a toroidal power transmission unit which generally comprises input and output cone discs which are coaxially arranged and power rollers which are interposed between the input and output cone discs.
For ease of description, the toroidal type continuously variable transmission will be referred to as torocoidal-type CVT hereinafter.
As a conventional torocoidal-type CVT which exhibits a powerful transmission of torque, Japanese Patent First Provisional Publication 2-163562 shows a dual cavity type which has two viz., front and rear toroidal power transmission units coaxially mounted therein and parallelly arranged in a power train. In the transmission of this publication, output cone discs of the front and rear units are integrally connected in a back-to-back connection manner and rotate freely about a main shaft in a transmission case, and input cone discs of the units are coaxially arranged to face the respective output cone discs and rotate together with the main shaft. By inputting a torque to the input disc of the front unit, rotation of both the input discs of the front and rear units is carried out. During this, a loading cam on the main shaft applies the input disc of the front unit with a biasing force in accordance with the transmission torque, so that the two input discs of the units are biased toward the respective output discs. With this, each power roller is compressed between the associated input and output discs by a force according to the transmission torque, so that power transmission between the associated input and output discs of each power transmission unit is carried out. That is, each power roller is frictionally engaged at diametrically opposed ends with the associated input and output discs. In operation, rotation of each input disc is transmitted to the associated power rollers and the rotation of each power roller is transmitted to the associated output disc. When, under this operation, an angle of each power roller relative to the main shaft is changed, a so-called power transmission ratio between the input and output discs of each power transmission unit is continuously changed. In the transmission, there is also employed a forward/backward mode switching mechanism by which the transmission can take forward and backward modes selectively. When, due to the work of the switching mechanism, the transmission takes the backward (or reverse) mode, a reverse sensor senses the reverse rotation transmission condition of the power transmission units and operates a switching device for forward/reverse speed change control valves. With this, the speed change control of the transmission is carried out by the reverse speed change control valve.
In the above-mentioned dual cavity type torocoidal-type CVT, output rotation of the transmission is taken out from a position between the two power transmission units. The output rotation is transmitted to a countershaft which is arranged offset and in parallel with the main shaft of the transmission. The rotation of the countershaft is then transmitted through a gear unit to a transmission output shaft which is coaxially arranged behind the rear power transmission unit. The reverse sensor is mounted to a leading end of the countershaft, which is remote from the gear unit.
When, in operation, the countershaft is rotated in a forward direction to move an associated motor vehicle forward, that is, when the transmission assumes a forward mode, a one-way clutch operates to disconnect the reverse sensor from the countershaft. While, when the countershaft is rotated in a backward direction to move the vehicle backward, that is, when the transmission assumes a backward mode, the one-way clutch operates to connect the reverse sensor with the countershaft. With this connection, the reverse sensor is driven by the countershaft and actuates the forward/backward mode switching mechanism in the above-mentioned manner.
Accordingly, there is a need of lubricating the reverse sensor particularly when the reverse sensor is driven by the countershaft. Japanese Patent First Provisional Publications 7-301300 and 7-293653 show measures for such lubrication. In the measure of 7-301300 publication, a so-called "oil splashing effect" of the gear unit on the countershaft is practically used. That is, the lubrication oil splashed by the gear unit on the countershaft is led to and reserved in a recessed high portion in the transmission, and the oil is naturally led to the reverse sensor through an axially extending oil passage formed in the countershaft. In the measure of 7-293653 publication, a force feed means is employed for enforcedly feeding the reverse sensor with lubrication oil through the axially extending oil passage of the countershaft. However, due to their inherent construction, the measures of these publications have failed to exhibit a satisfied result in lubricating the reverse sensor. That is, in the former measure, it is difficult to obtain a satisfied oil splashing effect in both a case wherein the countershaft is rotated in the forward direction and a cases wherein the countershaft is rotated in the backward direction. When the oil splashing effect is not effectively made, the recessed high portion in the transmission fails to reserve a satisfied amount of oil, which tends to cause poor lubrication of the reverse sensor. In the latter measure, due to the nature of the force feed means, a larger amount of oil is enforcedly led to the reverse sensor even when the sensor needs only a smaller amount of oil like in the case wherein the countershaft is rotated in the forward direction.